Voltage control system



Aug. 26, 1958 R. c. scoTT VOLTAGE CONTROL SYSTEM 3 Sheets-Sheet 1 Filed June 1, 1954 4 .1! lriiilllliiiit .INVENTOR.

336762716. 500254 BY WWW Aug. 26, 1958 R. c. SCOTT VOLTAGE CONTROL SYSTEM 5 Sheets-Sheet 2 Filed June 1, 1954 INVENTOI. arm C. oo/f United States Patent VOLTAGE CONTROL SYSTEM Richard C. Scott, Detroit, Mich., assignor to'The Udylite Corporation, Detroit, Mich., a corporation of Delaware Application June 1, 1954, Serial No. 433,655

3 Claims. (Cl. 204-198) The present invention pertains to voltage control in plating machines, such as those disclosed in the patents identified below. The invention is especially applicable to the problems involved in chromium plating.

Plating machines of this character are equipped with vertically movable cathode rail segments to lift the work out of the bath when it is to be transferred from one tank to another. On returning the work to the bath and also on alining and disalining the movable rail segments with the fixed cathode rail segments, certain conditions occur which are detrimental to the plating. One of these conditions obviously is arcing. i I

Other detrimental conditions are passivisation and bipolar effect. Although these terms are known in the art they will be defined briefly. When the work first engages the bath on being immersed, there is introduced an electrolytic cell between the work and the bath. The cell sets up a local reverse current which interferes with the plating, and this effect is known as passivisation. Also, on immersion opposite poles are formed on the work piece and bypass current on or in the piece. This action is known as bi-p olar eifect.

The principal object of the invention is to overcome these difliculties and is, accomplished essentially by applying auxiliary voltages at selected times in the cycle of operation. The voltages are applied from preferably three auxiliary voltage sources and are of such respective values as to offset the stated difficulties at the times when they would otherwise occur. The control of the auxiliary voltages is automatic and is effected by or related to the movement of components of the plating apparatus.

Figure 1 is a perspective view of the apparatus, showing the load ready to be lowered into the tanks and only the pre-strike voltage applied;

Figure 2 is a similar view showing the load lowered into the tanks and the plating voltage applied;

Figure 3 is a similar view after the work has been transferred orfshifted in the lower position and no auxiliary voltage applied; 1 w i a Figure 4'is a perspective. view showing the load lifted again in preparation for another cycle, and

.Figure S'is a detail perspective view illustrating the limit switch'roperating mechanism and the load advancing means. i

Refe'rence to these views will now be made by use of like characters which are employed to designate corresponding parts thr oughout In Fi ure '1 is'sh'ow eries of aimed plating tanks 1, 2 and 3 fitted witha pair of parallelanode rails 4 shown only in-tar k z forclc fness. Anode ibarsI5 are 'siis'pehded from the rails 4 in the usual manner. Between the r'ails.4 is a cathode. rail 6 for carryingthe work. The cathode rail system includes vertically movable segmentsfia and 6b at the end walls of the tanks forthe purpose of lifting work so that it may be transferred from one tank to the next. Mechanism for raising and loweringtheisegments isdi'sclosed in the United States. patents to J. V. Davis, No. 2,479,322 of August 16, 1949 andNo'. 2,650,600 of September 1', .1953. Workbooks 79areslidably suspended r 2,849,392 Patented, Aug. 26., 958

from the cathode railand are advanced on the rail by suitable means as known in the art and also shown in the aforementioned patents. A constant direct current at two to nine volts is supplied to the tanks from a suitable source by a positive line 8 connected to the anode rails 4 and a 'negative line 9 connected to the fixed segments of the cathode rail 6.

' Three separate sources of direct current, independently controlled, are provided for the purpose of supplementing the current from the line 8, 9 at specific intervals in the plating cycle. These sources are represented by rectifiers voltage of two to five volts; the source 11 is known as the plating rectifier (PLR) having an output voltage of two to nine volts; and the source 12 is known as the strike rectifier (SR) having an output voltage also of two to nine volts. An alternating current source has one side 13 con- :7" nected to corresponding intake terminals 101, 111 and 121 of the sources. The other side 14 of this source passes through a limit switch 15 from which it is continued by a conductor 141 to the remaining input terminal 102 of the source 10. Another conductor 16 from the output side of the limit switch 15 is joined to another limit switch 17 from which it is continued at 161 to a timer relay 18 at a.

terminal 181 thereof. The same terminal is joined by a '1 limit switch 15 and the limit switch 17.

. The output terminal 184 of the relay 18 is joined by a conductor 185 to the remaining terminal 122 of the source 12. Thus, the input source 12 is controlled by both limit switches and the timer relay.

The positive output terminals of the respective auxiliary sources are designated by the numerals 103, 113 and 123; and the negative .output terminals by the numerals 104, 114 and 124. .The terminals 103 and 113 are permanently joined by a bar 120 which also connects with the negative terminal 124 of source 12. The negative terminals 104 and114 are permanently joined by a 'bar or conductor The latter is engagea'ble by a complementary shoe contact 26 carried by themovable cathode rail segment 6b at a point thereof directly overthe forward end of the tank 2. A prolonged interval of contact-is" available at the members 22,23 duringthevertical movement but not at the oontacts 25,26- for a purpose that will presently be described. The positive output terminal .123. of the source 12 is connected by a conductor 27 to -the barB'. It is now cyident that'the-outputs of the sources 10 and '11" are connected in -parallel with each otherguand the :output of. the source 12 is I.c ori nected,in, series 1 thereto.f. Itris'aalso':

evident that a voltage oftw-oto nine volts is constantly iinpressegi on the-tank 2 from the source 8, 9 and: is supplemerited fromrthe'sourceslmdl and .12ithr0ugh operationof the various switching devices, as will be described.

r In the operation. o'fL-.th'e device, it will ber'ecalledthat and timer [8 is de-energized. Therefore, additional voltage is available only from the pre-strike source 10. The positive side of the circuit comprises terminal 103, bar 120, source 12 (merely as a path without addition of voltage) and-conductors 27'and 8 to the anode rails 4. The negative side comprises terminal 104, conductors 21, 22 and 23 to the load 6A. However, source is not eifective until load 6A engages the solution or strikes, at which time the pro-strike voltage of two to five volts is applied to load 6A. The effect of this pre-strike voltage which is less than plating voltage is to overcome passivisation and bi-polar effect.

When segments 6a and 6b with their loads 6A and 6B are fully descended as in Figure 2, switch 15 remains closed, while switch 17 closes by movement of parts and timer 18 goes into operation. Also, contact 26 comes into engagement with contact 25. All three sources 10, 11 and 12 are energized. Sources 10 and 12 deliver through the paths previously described. Source 11 is now active through its negative terminal 114 and bar 21 to contacts 22 and 23. Since the sources 10 and 11 are in parallel, their voltages do not accumulate, and the higher voltage of source 11 prevails. To this is added the voltage of the series connected source 12, so that four to eighteen volts are applied. It may be noted that timer 18 need not go on until segments 6a and 6b have actually alined with fixed segment 6, so that there is equal voltage throughout the alined segments and hence no arcing.

There is a dwell interval here in which the work is not shifted horizontally. The so-called strike voltage of four to eighteen volts is applied only temporaliy and is timed out, after proper duration, by the timer 18. The purpose of the strike voltage, which is approximately twice the normal plating voltage, is to cover areas that are hard to plate. The dwell interval is completed after source 12 has been timed out, thereby restoring the. normal plating voltage of two to nine volts.

At normal plating voltage the work is shifted horizontally to the position shown in Figure 3 by the aforementioned mechanical means. The-limit switches 15 and 17 are opened by moving parts and, with the timer 18 out, the sources 10, 11 and 12 are de-energized. Only source 8, 9 is effective. It will be seen that load 6A has moved from segment 6a to segment 6. Other work pieces 6C and 6D have been moved on to the segments 6a and 6b. Segments 6a and 6b are now raised to the position shown in Figure 4, also without arcing because of the uniform voltage throughout the cathode rail system. By pusher means of the character previously mentioned, loads 6C and 6D while elevated are shifted to the positions of loads 6A and 6B in Figure 1.. This mavement closes the limit switch 15 to start a new cycle from this position.

The means for operating the limit switches and ad vancing the work is illustrated in Figure 5. With respect to the segment 6a for example, there is a reciprocating work pusher bar 30 in the elevated position and a similar bar in the lower position as in the aforementioned patents. Each such bar carries pivoted pusher fingers 31 adapted to swing only when retracted and on forward movement to engage the hooks 7. The actuating member for the limit switch may be a rotary cog wheel 32 engageable by a switch tripper 32 on the bar 30 to open and close the switch at proper times as described.

Although the limit switches are operated from the respective bars 30, the timing is related functionally to the vertical movements of the segments 6a and 6b as set forth.

It is possible under favorable condition to omit the prestrike operation, thus eliminating the pre-strike rectifier. Also by a re-arrangement of the direct current constant source, this power supply can be substituted for the plating rectifier whereby the latter may also be omitted.

Although a specific embodiment of theinvention has 4. been illustrated and described, it will be understood that various alterations in the details of construction will be made without departing from the scope of the invention as indicated by the appended claims.

What I claim is:

1. In an apparatus for chrome plating a nickel-plated workpiece, a tank, an electrodein said tank, transporting means for moving the workpiecerelative to said tank including means for lowering the workpiece from a fully emersed position to a fully immersed position, first circuit means efifective while the workpiece is being lowered to said fully immersed positionfor establishing a potential difference of a first preselected finite amplitude between said electrode and the workpiece, second circuit means for establishing a potential difference of a second and different preselected finite amplitude between said electrode and the workpiece, third circuit'means for establishing a potential difierence of a third and still different preselected finite amplitude between said electrode and the workpiece, and means controlled by said transporting means and effective after the workpiece has been lowered to said fully immersedposition for successively enabling said second and third circuit means.

2. In an apparatus for chrome plating a nickel-plated workpiece, a tank, an electrode in said tank, transporting means for moving the workpiece relative to said tank including means for lowering the workpiece from-afully emersed position to a fullly immersed position, first circuit means effectiive while the workpiece is being lowered to said fully immersed position for establishing a potential difierence of a, first preselected finite. amplitude between said electrode and the workpiece, second circuit means for establishing a potential difference of 'a second preselected amplitudegreater than said first preselected amplitude between said electrodeand the workpiece, third circuit means for establishing a potentional-ditference of a third preselected amplitude intermediate said first and said second preselected ampltudes between said electrode and the worpiece, and means controlled by said transporting means and effective after the workpiece has been lowered to said fully immersed position for successivel-y enabling said second and third circuit means.

3. In an apparatus for chrome plating a nickel-plated workpiece, a tank, an electrode in said tank, transporting means for moving the workpiece relative to said tank including means for lowering the workpiece from a fully emersed position to a fully immersed position, first circuit means efiective While the workpiece is being lowered to said fully immersed position for establishing a potential difference of a first preselected finite aplitude between said electrode and the workpiece, second circuit means for establishing a potential difference of a second preselected ampltude between saidelectrode and the workpiece, switch means controlled by said transporting means and actuated after the workpiece has been lowered to said fully immersed position for enabling said second circuit means, additional circuit means for establishing a potential difference of a third preselected amplitude between said electrode and the workpiece, and means controlled by said switch means for enabling said additional circuit means a preselected time interval after the enabling of said second circuit means.

References Cited in the file of this patent UNITED STATES PATENTS 1,753,350 Schupp Apr. 8, 1930 1,959,764 Pothoff May 22, 1934 2,199,487 Etchison May 7, 1940 2,479,322 Davis Aug. 16, 1949 2,558,090 Jernstedt June 26, 1951 2,724,690 Soleck Nov. 22; 1955 2,724,691 Hakes Nov. 22, 1955 FOREIGN PATENTS 451,623 Germany-H, Oct. 29,. 1927. 

1. IN AN APPARATUS FOR CHOME PLATING A NICKEL-PLATED WORKPIECE, A TANK, AN ELECTRODE IN SAID TANK, TRANSPORTING MEANS FOR MOVING THE WORKPIECE RELATIVE TO SAID TANK INCLUDING MEANS FOR LOWERING THE WORKPIECE FROM A FULLY EMERSED POSITION TO A FULLY IMMERSED POSITION, FIRST CIRCUIT MEANS EFFECTIVE WHILE THE WORKPIECE IS BEING LOWERED TO SAID FULLY IMMERSED POSITION FOR ESTABLISHING A POTENTIAL DIFFERENCE OF A FIRST PRESELECTED FINITE AMPLITUDE BETWEEN SAID ELECTRODE AND THE WORKPIECE, SECOND CIRCUIT MEANS FOR ESTABLISHING A POTENTIAL DIFFERENCE OF A SECOND AND DIFFERENT PRESELECTED FINITE AMPLITUDE BETWEEN SAID ELECTRODE AND THE WORKPIECE, THIRD CIRCUIT MEANS FOR ESTABLISHING A POTENTIAL DIFFERENCE OF A THIRD AND STILL DIFFERENT PRESELECTED FINITE AMPLITUDE BETWEEN SAID ELECTRODE AND THE WORKPIECE, AND MEANS CONTROLLED BY SAID TRANSPORTING MEANS AND EFFECTIVE AFTER THE WORKPIECE HAS BEEN LOWERED TO SAID FULLY IMMERSED POSITION FOR SUCCESSIVELY ENABLING SAID SECOND AND THIRD CIRCUIT MEANS. 